The major objective of this research proposed are to study the chemistry, regulation and carcinogen binding properties of ligandin and investigate its role in hepatocarcinogenesis. The two different subunits of ligandin will be isolated and structure-function interrelationships will be explored by studying the effects of selective chemical modifications on binding, catalytic and immunological properties. The messenger RNA for ligandin will be purified by immunoprecipitation of polysomal RNA and saturation hybridization with total c-DNA as key steps. Purified mRNA will then be used for studying the regulation of synthesis of ligandin at transcriptional and translational levels as related to development, hepatoma, phenobarbitol administration and hypothyroidism. The covalent carcingoen binding to ligandin and its relation to hepatocarcinogenesis will be investigated by (a) isolation by isoelectricfocusing and studying the binding, catalytic and immunological properties of carcinogen bound ligandin, (b) determining if chemical carcinogens and their metabolites are conjugated to glutathione as mediated by ligandins catalytic activity, (c) determining the presence of ligandin by immunological and enzymatic methods and studying its carcinogen binding properties in normal, hepatoma and hybrid cell lines in culture.